The present disclosure relates to heart valve replacement and, more specifically, to devices and methods for implanting a collapsible prosthetic heart valve in a patient.
A healthy aortic valve acts as a one-way valve, opening to allow blood to flow out of the left ventricle of the heart, and then closing to prevent blood from flowing back into the heart. Diseased or damaged aortic valves may not close properly and thus allow blood to flow back into the heart. Damage to aortic valves may occur due to congenital defects, the natural aging process, infection or scarring. Diseased or damaged aortic valves sometimes need to be replaced to prevent heart failure. In such cases, collapsible prosthetic heart valves may be used to replace the native aortic valve.
Current collapsible prosthetic heart valve designs may be used in high-risk patients who may need a cardiac valve replacement, but who are not appropriate candidates for conventional open-chest, open-heart surgery. These collapsible and re-expandable prosthetic heart valves can be implanted transapically or percutaneously through the arterial system. One percutaneous delivery method entails introducing a collapsible prosthetic heart valve through a patient's femoral artery. This delivery method is referred to as a transfemoral approach.
A collapsible prosthetic heart valve may be delivered into a patient via a tube-like delivery apparatus such as a catheter, a trocar, a laparoscopic instrument, or the like. To place such a valve into a delivery apparatus and ultimately into a patient, the valve must first be collapsed or crimped to reduce its circumferential size. The delivery apparatus is then introduced transapically or percutaneously into a patient until it reaches the implant site.
When a collapsed heart valve has reached the desired implant site in the patient (e.g., at or near the annulus of the patient's heart valve that is to be replaced by the prosthetic valve), the prosthetic heart valve can be released from the delivery apparatus and re-expanded to its full operating size.
As stated above, collapsible prosthetic heart valves may be delivered to the valve annulus, and particularly the aortic valve annulus, either transfemorally or transapically. With either technique, however, it is difficult to properly align the collapsible heart valve with the valve annulus.
In transfemoral valve implantation, the collapsible prosthetic heart valve is delivered in a retrograde manner from the femoral artery through the aortic arch A to the native aortic valve annulus, as seen in FIG. 1. During delivery, the distal sheath 12 of the delivery device 10 is bent significantly to pass through the aortic arch A, which significantly biases the sheath toward the outside wall of the aortic arch. When the distal sheath passes through the aortic arch A and enters the left ventricle, it may exert a force on the septum wall S of the heart, as seen in FIG. 1. Depending on the bending angle of the aortic arch A and the stiffness of the outer shaft 14 of the delivery device 10, the distal sheath 12 may exert as much as 1 pound of force on the septum wall S of the heart. This excessive force could affect the electrical conduction system of the heart. For instance, an excessive force on the septum wall S of the heart may cause arrhythmic conditions (i.e., irregular cardiac rhythm), such as a ventricular fibrillation during the valve implantation or an atrioventricular block after implantation.
It is therefore desirable to reduce the force exerted on the septum wall S of the heart during valve implantation. To address this issue, the stiffness of the delivery catheter shaft could be decreased. However, reducing the stiffness of the delivery catheter shaft would likely sacrifice at least some of the columnar strength necessary for deployment and resheathing. Another possible solution is to employ a steerable catheter. Steerable catheters, however, can be bulky, expensive to make and more complicated to use. It is therefore desirable to have devices and methods which can effectively deliver and deploy a prosthetic heart valve without significantly changing the delivery device.